CN103200665A - Minizone synchronization method and device for time division duplexing (TDD) system base station - Google Patents

Abstract

The invention discloses a method and a device for synchronizing between base stations of a TDD system. The method includes: the mobile terminal keeps synchronization with the clock reference base station, and measures the synchronization error between it and the secondary base station; the mobile terminal sends the measured synchronization error to the secondary base station, so that the secondary base station according to the Synchronization processing is performed according to the above synchronization error. Adopting the present invention can solve the problem that the traditional air interface synchronization solution cannot realize the synchronization between cells in different-frequency networking without introducing new hardware costs.

Description

Method and device for inter-cell synchronization of base station in TDD system

technical field

The invention relates to the field of communication technology, in particular to a method and device for synchronizing between base station cells of a TDD system.

Background technique

The TDD (Time Division Duplexing, Time Division Duplexing) system transmits and receives signals in the same frequency band. If synchronization is not maintained between cells, there will be a serious problem of mutual interference between the sending and receiving time slots. Therefore, when deploying a TDD network, it is necessary to maintain accurate synchronization of subframe boundaries between cells, and configure the same ratio of uplink and downlink time slots in the same TDD synchronization area.

There are mainly three types of existing inter-cell synchronization schemes:

(1) Satellite synchronization, using GPS (Global Positioning System, Global Positioning System) or Beidou system

Use satellite receivers to obtain high-precision frequency and time synchronization reference signals through satellite timing, and use this reference synchronization signal to periodically adjust the local frequency and time of the base station.

(2) Network synchronization

Usually refers to synchronization using the IEEE1588 protocol, which is a precise time synchronization protocol that provides frequency and time synchronization information for base stations through a fixed transmission network via the 1588v2 high-precision time synchronization protocol. It is a timing transmission mechanism specially designed for packet networks. It adopts time distribution mechanism and time scheduling concept to correct local time information and maintain synchronization with the synchronization source in the synchronization network.

(3) Air interface synchronization

The main idea is that the base station listens to the synchronization signal of the reference base station that has achieved absolute time synchronization through the periodic air interface, and measures the propagation delay through random access requests to achieve frequency and time synchronization with the reference base station. This solution is usually used in small cellular base stations such as Femto base stations.

The above-mentioned satellite synchronization scheme is an absolute time synchronization scheme with the highest synchronization accuracy and is not affected by the networking mode and transmission network, but it needs to deploy satellite receivers and satellite receiving antennas at the base station, which introduces additional hardware costs; on the other hand , when this scheme is applied to an indoor base station, it will be affected by the occlusion or shielding of the satellite signal in the indoor environment, and the synchronization signal cannot be obtained when the satellite signal is weak.

The above network synchronization scheme requires that the entire transmission link and the base station support the IEEE1588 protocol. In terms of the transmission network, the existing transmission network does not support the IEEE1588 protocol to a high degree. If support is required, the cost of transmission network construction and maintenance will be increased; the base station requires IEEE1588 special protocol The processing chip may occupy the processing resources of the baseband processing chip of the base station. It is restricted by two aspects from the transmission network and the base station.

The above air interface synchronization solution does not require the introduction of hardware costs such as satellite receivers or IEEE1588 protocol processing chips on the base station side, nor does it require the cooperation of the transmission network. However, this solution requires the synchronization source base station (primary base station) and the air interface listening base station (slave base station) to work in the same frequency band, otherwise the air interface synchronization signal cannot be intercepted.

In the actual TDD network, there are likely to be a large number of base stations with different working frequency bands (that is, different frequency networking, such as TD-LTE outdoor frequency band 2.6GHz, indoor 2.3GHz), if the base station does not support multi-band receivers, it cannot be synchronized through the traditional air interface The scheme realizes inter-cell synchronization of different base stations; if base stations in different frequency bands are required to achieve inter-cell synchronization, all base stations are required to support multi-band reception or adopt satellite synchronization or network synchronization solutions, which will introduce additional hardware costs.

Contents of the invention

Embodiments of the present invention provide a method and device for inter-cell synchronization of a TDD system base station, which are used to solve the problem that the traditional air interface synchronization scheme cannot achieve inter-cell synchronization in different-frequency networking without introducing additional hardware costs.

The method for synchronizing between cells of a TDD system base station provided in an embodiment of the present invention includes:

The mobile terminal maintains synchronization with the clock reference base station, and measures the synchronization error between it and the secondary base station;

The mobile terminal sends the measured synchronization error to the secondary base station, so that the secondary base station performs synchronization processing according to the synchronization error.

Another TDD system inter-cell synchronization method provided by this embodiment includes:

receiving a synchronization error between the mobile terminal and the secondary base station measured and sent by the mobile terminal from the base station; wherein the mobile terminal is synchronized with the clock reference base station;

The secondary base station performs synchronization processing according to the synchronization error.

The mobile terminal provided by the embodiment of the present invention includes:

a synchronization module for maintaining synchronization with a clock reference base station;

A measurement module, used to measure the synchronization error between the mobile terminal and the secondary base station;

A reporting module, configured to send the measured synchronization error to the secondary base station, so that the secondary base station performs synchronization processing according to the synchronization error.

The base station equipment provided by the embodiment of the present invention includes:

A receiving module, configured to receive a synchronization error between the mobile terminal and the secondary base station measured and sent by the mobile terminal; wherein the mobile terminal is synchronized with the clock reference base station;

A synchronization module, configured to perform synchronization processing according to the synchronization error.

In the above embodiments of the present invention, the multi-mode terminal is synchronized with the master base station, and at the same time, the multi-mode terminal measures the synchronization error with the slave base station and reports it to the slave base station, so that the slave base station is synchronized with the multi-band terminal, Since the multi-band terminal keeps synchronization with the master base station, and the multi-band terminal can measure the synchronization error with the slave base stations of different frequency bands, the synchronization between the slave base stations of different frequency bands and the master base station is realized.

Description of drawings

FIG. 1 is a schematic diagram of a different-frequency networking architecture in an embodiment of the present invention;

FIG. 2 is a schematic flow diagram of a mobile terminal searching for a primary base station cell in an embodiment of the present invention;

FIG. 3 is a schematic flow diagram of a mobile terminal searching for a secondary base station cell in an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a mobile terminal provided by an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a base station device provided by an embodiment of the present invention.

Detailed ways

The embodiment of the present invention is based on the realization principle of traditional air interface synchronization, and measures cells of different frequency bands by means of multi-band terminals in overlapping coverage areas of cells of different frequency bands, thereby realizing inter-cell synchronization in inter-frequency networking.

Usually, the hardware design of the mobile terminal considers supporting multiple frequency bands (that is, working in different frequency bands), so there is no need to introduce additional hardware costs for the base station and the mobile terminal.

Embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

Referring to FIG. 1 , it is a schematic diagram of an inter-frequency networking architecture provided by an embodiment of the present invention. Wherein, the master base station and the slave base station work in different working frequency bands, and the mobile terminal supports multiple frequency bands. A mobile terminal (the mobile terminal supports multiple frequency bands) within the overlapping coverage area of the master base station cell and the slave base station cell can communicate with the master base station or with the slave base station. The primary base station is a clock reference base station, and usually a base station that can receive GPS signals or obtain a sufficient synchronization source is used as a clock reference base station, so as to be able to maintain synchronization with GPS or a synchronization source. The primary base station includes but is not limited to a macro base station, and the secondary base station includes but not limited to a femtocell base station or a femto base station or other microcell base station.

In the embodiment of the present invention, the mobile terminal periodically maintains synchronization with the main base station, that is, the terminal establishes synchronization with the main base station that has achieved absolute time synchronization through measurement and performs periodic synchronization maintenance. The implementation process can adopt the existing technology.

Specifically, the mobile terminal performs cell search by acquiring three physical signals during initial access or cell handover, and after completing the cell search, the mobile terminal can realize synchronization with the master base station. These three signals are primary synchronization signal, secondary synchronization signal and downlink pilot signal. As shown in Figure 2, the cell search process of the mobile terminal may generally include:

In step 201, the mobile terminal receives a signal at a central frequency point where a primary base station cell may exist, and judges whether there may be a base station cell around this frequency band based on the signal reception strength.

Step 202, the mobile terminal receives the primary synchronization signal around the central frequency band, obtains the cell ID based on it, determines the time slot boundary of 5 ms, and obtains the CP (cyclic prefix) length.

Step 203, after 5ms time slot synchronization, the mobile terminal searches forward for the secondary synchronization signal on the basis of the primary synchronization signal, and determines the 10ms boundary after receiving the secondary synchronization signal to achieve the purpose of frame synchronization, and determines the cell together with the primary synchronization signal Physical layer ID (cell ID).

Step 204, the mobile terminal reads the PBCH (Physical Broadcast Channel, physical broadcast channel), demodulates to obtain the downlink pilot signal, and performs more accurate time/frequency synchronization according to the downlink pilot signal.

In order to further improve the synchronization accuracy, the mobile terminal can measure its transmission delay with the primary base station through a random access process. For example, according to the time when the random access request is sent and the time when the random access response is received from the main base station, the transmission delay with the main base station is calculated. When synchronizing with the main base station, the synchronization error with the base station is corrected according to the transmission time delay, and synchronization processing is performed according to the corrected synchronization error to realize time/frequency synchronization with the main base station.

Thereafter, the mobile terminal can periodically measure the primary synchronization signal, secondary synchronization signal and downlink pilot signal, and maintain time/frequency synchronization with the primary base station according to the time/frequency synchronization information carried in the measured signals. Furthermore, in the process of periodically maintaining synchronization with the master base station, the transmission delay between it and the master base station (the transmission delay is measured through the random access process) can be considered, that is, according to the measured time/frequency synchronization information and the transmission delay, determine the synchronization error between it and the primary base station, and use this to perform time/frequency synchronization.

Based on the above network architecture, the synchronization process between base station cells of the TDD system implemented by mobile terminals in the overlapping coverage area with the cell of the primary base station and the cell of the secondary base station can be shown in FIG. 3 . When the mobile terminal enters the overlapping coverage area of the main base station cell and the secondary base station cell, its cell search and synchronization process can be shown in Figure 3, including:

Step 301, the mobile terminal searches for the primary synchronization signal, secondary synchronization signal, and downlink pilot signal on the central frequency point where the secondary base station cell may exist, and obtains the time/frequency synchronization information carried in it according to the searched signal, and based on these information Calculate the time/frequency synchronization error between the slave base station and the local clock of the mobile terminal.

Step 302, the mobile terminal reports the measured synchronization error to the secondary base station.

Specifically, the mobile terminal may report the measured time/frequency synchronization error to the secondary base station through a specified channel or a specified message. For example, the mobile terminal can send a measurement report to the secondary base station through PUCCH (Physical Uplink Control Channel, Physical Uplink Control Channel) or PUSCH (Physical Uplink Shared Channel, Physical Uplink Shared Channel), which carries the measured time/frequency synchronization error.

Step 303, the secondary base station performs synchronization processing according to the synchronization error reported by the mobile terminal, so as to eliminate the synchronization error between the base station and the mobile terminal.

Specifically, the secondary base station can correct the frequency and phase of the local clock to eliminate the synchronization time/frequency error.

In order to further improve the synchronization accuracy, during the initial access process of the mobile terminal to the secondary base station, the mobile terminal can measure its transmission delay with the secondary base station according to the random access process, and when calculating its time synchronization error with the secondary base station, it can be based on After calculating the time synchronization error from the received signal, the transmission time delay is used to correct the time synchronization error, and then the corrected synchronization error is reported to the secondary base station.

After initially accessing the secondary base station, the mobile terminal periodically measures the synchronization error between it and the secondary base station (the specific implementation process is similar to the measurement process when initially accessing the secondary base station), and reports the measured synchronization error to the secondary base station, So that the secondary base station performs time/frequency synchronization according to the synchronization error. Preferably, the time synchronization error periodically reported by the mobile terminal to the secondary base station is a synchronization error corrected according to the transmission time delay between the mobile terminal and the secondary base station.

There may be multiple mobile terminals in the overlapping area of the primary base station and the secondary base station. After measuring the synchronization error between them and the secondary base station, these mobile terminals will report the measured synchronization error to the secondary base station. In order to improve the synchronization accuracy of the slave base station, the slave base station can average the synchronization errors reported by each mobile terminal, and then adjust the local clock of the slave base station according to the synchronization error obtained by the average operation to eliminate the synchronization error, so as to realize the synchronization with the master base station time/frequency synchronization between

Among them, there may be various algorithms used when the base station averages the synchronization errors reported by each mobile terminal, for example, arithmetic average value, weighted average, etc. When using the weighted average algorithm, its weighting coefficient can be determined according to the channel quality or signal strength or distance between each mobile terminal and the secondary base station, or it can be determined by combining the above factors, for example, the worse the channel quality, the weaker the signal strength or the shorter the distance. The farther the mobile terminal is, the smaller the corresponding weighting factor is. Among them, the channel quality can be measured by SINR (Signal to Interference plus Noise Ratio, signal to interference plus noise ratio), the signal strength can be measured by RSRP (Reference Signal Receiving Power, reference signal received power), and the distance can be measured by TA (Timing Advance, time advance) measure.

It can be seen from the above description that the embodiment of the present invention does not need to modify or upgrade the hardware of the primary base station, secondary base station, and mobile terminal, and the synchronization between base station cells in the case of inter-frequency networking can be realized by using the characteristics of the mobile terminal supporting multiple frequency bands. Compared with the traditional air interface synchronization scheme, the embodiment of the present invention can solve the problem that inter-cell synchronization cannot be realized during inter-frequency networking; compared with the satellite synchronization scheme, there is no need to increase hardware equipment such as satellite receivers and antennas, and the hardware cost of the base station is not increased; The network synchronization solution does not require transmission network equipment to support network synchronization protocols, and there is no requirement for transmission equipment.

It should be noted that, the above-mentioned embodiment is described by taking the mobile terminal periodically maintaining synchronization with the primary base station, and the mobile terminal periodically measuring and sending the synchronization error between itself and the secondary base station as an example. Those skilled in the art should understand that if a single The object of the present invention can also be achieved to a certain extent by performing operations related to synchronization, measuring and sending synchronization errors.

Based on the same technical concept, the embodiment of the present invention also provides a mobile terminal and base station equipment applicable to the above process.

Referring to FIG. 4 , it is a schematic structural diagram of a mobile terminal provided by an embodiment of the present invention. As shown in the figure, the mobile terminal may include:

The synchronization module 401 is used to keep synchronized with the clock reference base station; preferably, this module can periodically keep synchronized with the clock reference base station;

The measurement module 402 is used to measure the synchronization error between the mobile terminal and the secondary base station; preferably, this module can periodically measure the synchronization error between the mobile terminal and the secondary base station;

The reporting module 403 is configured to send the measured synchronization error to the secondary base station, so that the secondary base station performs synchronization processing according to the synchronization error. Preferably, the module can periodically send the measured synchronization error to the secondary base station.

The synchronization error sent by the reporting module 403 to the secondary base station includes a time synchronization error, and the mobile terminal further includes: a correction module 404, which is used to measure the time synchronization between the mobile terminal and the secondary base station in the measurement module 402 After the error, the time synchronization error is corrected according to the transmission delay between the mobile terminal and the secondary base station. Correspondingly, the time synchronization error sent by the reporting module 403 to the secondary base station is a corrected time synchronization error.

Specifically, the synchronization module 401 measures the synchronization error between the mobile terminal and the clock reference base station, and after measuring the synchronization error between the mobile terminal and the clock reference base station, according to the synchronization error between the mobile terminal and the clock reference The synchronization error is corrected with reference to the transmission time delay between the base stations, and synchronization is performed with the clock reference base station according to the corrected synchronization error.

Referring to FIG. 5 , it is a schematic structural diagram of a base station device provided by an embodiment of the present invention, and the base station is a slave base station in the above process. As shown in the figure, the base station equipment may include:

The receiving module 501 is configured to receive the synchronization error between the mobile terminal and the secondary base station measured and sent by the mobile terminal; wherein the mobile terminal is synchronized with the clock reference base station;

The synchronization module 502 is configured to perform synchronization processing according to the synchronization error.

In the case where the receiving module 501 receives the synchronization errors sent by at least two mobile terminals, the base station equipment further includes: a correction module 503, configured to average the synchronization errors sent by the at least two mobile terminals, The averaging algorithm adopted can be the same as that mentioned above. Correspondingly, the synchronization module 502 may perform synchronization processing according to the averaged synchronization error.

The synchronization error received by the receiving module 501 includes a time synchronization error, and the time synchronization error is a time synchronization error corrected by the mobile terminal according to the transmission delay between itself and the secondary base station.

Preferably, the receiving module 501 can receive the synchronization error between the mobile terminal and the secondary base station which is periodically measured and sent by the mobile terminal; wherein, the mobile terminal is periodically synchronized with the clock reference base station.

It should be recognized that the various modules of the device of the present invention can be integrated into one body, or deployed separately. The above modules can be combined into one module, or can be further split into multiple sub-modules.

Through the description of the above embodiments, those skilled in the art can clearly understand that the present invention can be implemented by means of software plus a necessary general-purpose hardware platform, and of course also by hardware, but in many cases the former is a better implementation Way. Based on this understanding, the essence of the technical solution of the present invention or the part that contributes to the prior art can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions to make a A computer device (which may be a personal computer, a server, or a network device, etc.) executes the methods described in various embodiments of the present invention.

Those skilled in the art can understand that the drawing is only a schematic diagram of a preferred embodiment, and the modules or processes in the drawing are not necessarily necessary for implementing the present invention.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (16)

1. method for synchronous between a TDD system base station cell is characterized in that this method comprises:

Portable terminal and clock reference base station keep synchronously, and measure it and from the synchronous error between the base station;

Described portable terminal sends to the synchronous error that measures described from the base station, so that describedly handle synchronously from the base station according to described synchronous error.

2. the method for claim 1 is characterized in that, described portable terminal sends to and describedly comprises time synchronization error from the synchronous error of base station;

Described portable terminal also comprises: according to described portable terminal and the described described time synchronization error of propagation delay time correction between the base station after measuring itself and described time synchronization error between the base station;

It is revised time synchronization error that described portable terminal sends to described time synchronization error from the base station.

3. method as claimed in claim 1 or 2 is characterized in that, described portable terminal and clock reference base station keep comprising synchronously:

Described portable terminal is measured the synchronous error between itself and the described clock reference base station, and after the synchronous error that measures between itself and the described clock reference base station, according to the described synchronous error of propagation delay time correction between itself and the described clock reference base station, carry out synchronously according to revised synchronous error and described clock reference base station.

4. method as claimed in claim 1 or 2 is characterized in that, described mobile terminal period and clock reference base station keep synchronously, and period measurement itself and from the synchronous error between the base station;

Described mobile terminal period sends to the synchronous error that measures described from the base station.

5. TDD system base-station inter-cell synchronization method is characterized in that this method comprises:

Described portable terminal and described synchronous error between the base station from base station mobile terminal receive measure and transmit; Wherein, described portable terminal and clock reference base station keep synchronously;

Describedly handle synchronously from the base station according to described synchronous error.

6. method as claimed in claim 5, it is characterized in that, under the described situation that receives the synchronous error that at least 2 portable terminals send from the base station, this method also comprises: the described synchronous error that described at least 2 portable terminals is sent from the base station averages processing;

Described from the base station synchronous error after according to average treatment handle synchronously.

7. as claim 5 or 6 described methods, it is characterized in that described portable terminal sends to and describedly comprises time synchronization error from the synchronous error of base station;

Described portable terminal sends to described time synchronization error from the base station, is described portable terminal according to itself and the described revised time synchronization error of propagation delay time between the base station.

8. as claim 5 or 6 described methods, it is characterized in that described described portable terminal and described synchronous error between the base station from base station mobile terminal receive period measurement and transmission; Wherein, described portable terminal and clock reference base station keep synchronously.

9. a portable terminal is characterized in that, comprising:

Synchronization module is used for keeping synchronously with the clock reference base station;

Measurement module is for this portable terminal of measurement and from the synchronous error between the base station;

Reporting module, be used for the synchronous error that measures is sent to described from the base station so that describedly handle synchronously from the base station according to described synchronous error.

10. portable terminal as claimed in claim 9 is characterized in that, described reporting module sends to and describedly comprises time synchronization error from the synchronous error of base station, and described portable terminal also comprises:

Correcting module is used for after described measurement module measures this portable terminal and described time synchronization error between the base station, according to this portable terminal and the described described time synchronization error of propagation delay time correction between the base station;

It is revised time synchronization error that described reporting module sends to described time synchronization error from the base station.

11. as claim 9 or 10 described portable terminals, it is characterized in that, described synchronization module specifically is used for, measure the synchronous error between this portable terminal and the described clock reference base station, and after the synchronous error that measures between this portable terminal and the described clock reference base station, according to the described synchronous error of propagation delay time correction between this portable terminal and the described clock reference base station, carry out synchronously according to revised synchronous error and described clock reference base station.

12. as claim 9 or 10 described portable terminals, it is characterized in that described synchronization module specifically is used for, cycle and clock reference base station keep synchronously;

Described measurement module specifically is used for, this portable terminal of period measurement and from the synchronous error between the base station;

Described reporting module specifically is used for, and the cycle sends to the synchronous error that measures described from the base station, so that describedly handle synchronously from the base station according to described synchronous error.

13. a base station equipment is characterized in that, comprising:

Receiver module is for described portable terminal and the described synchronous error between the base station of mobile terminal receive measure and transmit; Wherein, described portable terminal and clock reference base station keep synchronously;

Synchronization module is used for handling synchronously according to described synchronous error.

14. base station equipment as claimed in claim 13 is characterized in that, receives at described receiver module under the situation of the synchronous error that at least 2 portable terminals send, described base station equipment also comprises:

Correcting module is used for the synchronous error that described at least 2 portable terminals send is averaged processing;

Described synchronization module specifically is used for, and handles synchronously according to the synchronous error after the average treatment.

15. as claim 13 or 14 described base station equipments, it is characterized in that, comprise time synchronization error in the synchronous error that described receiver module receives, described time synchronization error is that described portable terminal is according to own and the described revised time synchronization error of propagation delay time between the base station.

16. as claim 13 or 14 described base station equipments, it is characterized in that described receiver module specifically is used for, mobile terminal receive period measurement and the described portable terminal and the described synchronous error between the base station that send; Wherein, described mobile terminal period and clock reference base station keep synchronously.

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